During the catalytic cracking process (FCC) an attempt is made to avoid the harmful effect that several compounds, such as azotic compounds and metals, especially vanadium, which are contained in feed, exert on the catalyst. All along the process of reactions that take place in the riser, these compounds are deposited on the catalyst that becomes either reversibly or irreversibly, poisoned through their action over its most active ingredient, zeolite, while the active centres or their structure are respectively poisoned or destroyed. There are two possible solutions to avoid this danger. The first one consists in a hydro-treatment of the power supply to the FCC, This solution, although quite effective, is very seldom put into practice due to its high price. The second alternative entails the incorporation of additives into the catalyst as components ready to be sacrificed while strongly interacting with the poisons.
In the case of poisoning through azotic compounds present in the feed, these are very actively adsorbed, if they are of a basic character, on the acid centres of zeolite, making the catalyst activity rapidly diminish; this effect is much more notorious in catalysts containing highly stable zeolite of a low cell unit (A. Corma, V. Fornes, J. B. Monton and A. V. Orchilles, Ind. Eng. Chem. Res., 26, 882 (1987); Scherzer and O. P. McArthur, Ind. Eng. Chem. Res. 27, 1571 (1988). The harmful effect of the basic azotic compounds may be reduced by the use of active matrices of aluminum or silica-aluminum which, apart from providing an additional activity to that of zeolite, have also the ability to capture the nitrogen compounds (L. D. Silverman, S. Winkler, J. A. Tiethof and A. Witoshkin AM-86-62 NPRA Annual Meeting Mar. 23-25 (1986); J. E. Otterstedt, S. B. Gevert S. Jaras and P. G. Menon, Appl. Catal. 22, (1986); J. E. Otterstedt, Y. M. Zhu and J. Sterte, Appl. Catal. 38, 143 (1988); B. K. Speronello and G. W. Young, Oil .sctn. Gas J. 82, 139 (1984).
A new material derived from sepiolite has recently been presented. It possesses acid properties and may be used as an active component of a FCC catalyst (A. Corma, V. Fornes, A. Mifsud and J. Perez Pariente, Clay Minerals 19, 673,(1984) ibid ACS Syrup. Ser. 452 (Fluid Catalytic Cracking II), 293 (1990.)
The present patent of invention shows how an aluminum sepiolite of the type described in the two above-mentioned works, can be used as a matrix component for the purpose of passifying the nitrogenous compounds responsible for the poisoning of zeolite, and may favourably compete with the more effective materials used so far, such as silica-alumina.